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PLoS One. 2019 May 21;14(5):e0216581. doi: 10.1371/journal.pone.0216581. eCollection 2019.

Influence of a Serratia marcescens outbreak on the gut microbiota establishment process in low-weight preterm neonates.

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Servicio de Neonatología, Hospital Universitario La Paz, and Universidad Autónoma de Madrid, Madrid, Spain.
Servicio de Microbiología y Parasitología, Hospital Universitario Ramón y Cajal, and Instituto Ramón y Cajal de Investigaciones Sanitarias (IRYCIS), Madrid, Spain.
Departamento de Bromatología, Facultad de Veterinaria Nutrición y Ciencia de los Alimentos, Universidad Complutense de Madrid, Madrid, Spain.
Servicio de Microbiología, Hospital Universitario La Princesa, and Universidad Autónoma de Madrid, Madrid, Spain.
Servicio de Microbiología, Hospital Universitario La Paz, Madrid, Spain.
Red de Salud Materno Infantil y del Desarrollo, Instituto de Salud Carlos III, Madrid, Spain.


Adequate gut microbiota establishment is important for lifelong health. The aim was to sequentially analyze the gut microbiota establishment in low-birth-weight preterm neonates admitted to a single neonatal intensive care unit during their first 3 weeks of life, comparing two epidemiological scenarios. Seven control infants were recruited, and another 12 during a severe S. marcescens outbreak. Meconium and feces from days 7, 14, and 21 of life were collected. Gut microbiota composition was determined by 16S rDNA massive sequencing. Cultivable isolates were genotyped by pulsed-field gel electrophoresis, with four S. marcescens submitted for whole-genome sequencing. The expected bacterial ecosystem expansion after birth is delayed, possibly related to antibiotic exposure. The Proteobacteria phylum dominates, although with marked interindividual variability. The outbreak group considerably differed from the control group, with higher densities of Escherichia coli and Serratia to the detriment of Enterococcus and other Firmicutes. Curiously, obligate predators were only detected in meconium and at very low concentrations. Genotyping of cultivable bacteria demonstrated the high bacterial horizontal transmission rate that was confirmed with whole-genome sequencing for S. marcescens. Preterm infants admitted at NICU are initially colonized by homogeneous microbial communities, most of them from the nosocomial environment, which subsequently evolve according to the individual conditions. Our results demonstrate the hospital epidemiology pressure, particularly during outbreak situations, on the gut microbiota establishing process.

Conflict of interest statement

The authors have declared that no competing interests exist.

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